Try to create long matches to earn higher bonuses for those elements. It is possible to get up to 100%. This becomes useful when you must destroy asteroids or collect a specific number of elements. Ignore a particular element for a few matches to let that type of element to fill the board. This will in turn make it easier for you to create a very long match, which in turn will increase your bonus. Consider matching one or two types of elements to allow the board to be filled with what is needed.